1. Field of the Invention
The invention is an optical prism module, particularly related to a fingerprint recognition equipment, for light transmission.
2. Descriptions of the Related Art
Typically, a conventional optical fingerprint image acquisition device may be composed of a prism, a convex lens, an image sensor and a light source generally, in which the prism is arranged as an inverted triangle, the convex lens corresponds to a first side of the prism, the image sensor is in correspondence with the convex lens, and the light source corresponds to a second side of the prism.
In use, an operator is allowed to place fingerprint on a third side of the prism while the light source performs irradiation from the second side of the prism and a light ray is reflected to the first side of the prism by a fingerprint image, and in turn, the light enters the convex lens, followed by focusing on the image sensor to, thereby, perform fingerprint recognition.
However, for the above conventional optical fingerprint image acquisition device, the volume of the prism thereof is usually constrained to shape and cannot be reduced, such that it cannot be employed on current compact electronic devices effectively.
In order to overcome the disadvantages of traditional optical fingerprint image acquisition devices, related patents are proposed, such as P.R.C. invention patent publication No. CN101034437A, “Fingerprint Collecting Method and High-Resolution Thin Type Fingerprint Collector”, which figures out existing issues of current technologies, including small acquisition and poor definition in existing technology. For its method, the light source is irradiated to the prism bottom through the prism, the fingerprint under the prism bottom reflects to reflection the prism oblique of the lumbar reflection mirror and black-paint film on the prism bottom, the fingerprint images on reflective mirror and black paint film project on the photoelectric detector through the back of prism and the projection lens. Collector is composed of the light source, a right angle trapezoidal prism which bottom longitudinal cross section greater than hight, lens and photo-electric detector; lens and photo-electric detector configurating in the back-side of prism, the ramp lumbar of prism having a reflector surface, a viewfinder with oblique configuration on the lateral of lens, the photoelectric detector above viewfinder, the characteristic is that the bottom of the prism is painted black, black paint layer and reflector mirror as a reflector surface. The method has the advantages of a larger fingerprint reflector, a greater acquisition area and high definition. Collector of small size, light weight, large area of collected fingerprint image, high clarity, collector and prism to achieve ultra-thin, is convenient to match with mouse, keyboard, door locks, cars, mobile phones and other equipments of space-constrained installation for use.
Additionally, P.R.C. invention patent publication No. CN CN102004912 B, “Fingerprint Acquisition Device”, comprises a light source, a prism, a light detector and an image sensor. The prism has a fingerprint acquisition surface, a reflection surface and an outgoing surface. The light detector is provided with a lens, and reflectors which are respectively arranged between the outgoing surface and the lens and between the lens and the image sensor. Light emitted by the light source is incident upon the prism, and light emitted by the outgoing surface is detected in the observation angle range and transmitted to the image sensor. The reflection surface is not symmetric relative to the observation shaft of the light detector, such that the light exits from one angle of the prism, and the path of light is refracted back to spare space at one side of the prism through the reflection of the reflectors. Thus, it has the advantage of reducing volume, and fitting product miniaturization tendency.
The light enters the prism, followed by outputting to the photoelectric detector with reflection for reducing a single optical path to reducing the volume of the fingerprint collection device in the patents mentioned above. By such an approach may improve shortages of traditional optical fingerprint image acquisition devices. However, those prisms with one reflection optical path still cannot satisfy current electronic products that are miniaturized (thinned) increasingly. Therefore, such various conventional products are still insufficient in real applications.
In view of this, the inventor of the present invention has researched and developed an optical prism module with efforts in order to improve various shortages of above conventional technologies.